(1) Field of the Invention
This invention relates, in general, to material treatment systems that employ a gaseous medium to fluidize particles in heat exchange or other treating relation More particularly, the invention relates to improved apparatus for bringing the gaseous medium into contact with the particulate material and for fluidizing the particles. Even more particularly, it relates to a nozzle assembly of particular configuration for bringing a gaseous medium into contact with, and for the fluidization of, particulate material.
(2) Description of the Prior Art
Particulate material is advantageously treated by maintaining the particles in fluidized condition as they are transported by a conveyor continuously through a particle treatment zone. Thus, in the food industry, nuts, cocoa beans, grains, and cereals are subjected to roasting, drying or cooling treatments, as desired, and vegetables such as peas and beans are dehydrated. And, plastic and rubber particles, etc. are treated for industrial purposes.
The particles in such treatments are fluidized, in general, by a plurality of gaseous jets which discharge from cylindrical-shaped tubes which extend vertically downwardly toward the imperforate base member of the conveyor, as disclosed in my U.S. Pat. No. 3,060,590, which issued Oct. 30, 1962. Examples of other prior art patents disclosing this manner of fluidization are U.S. Pat. Nos. 3,262,217; 3,398,467; 4,109,394; 4,169,322; and 4,201,499.
Although the particle fluidization and treatment as accomplished in the above-mentioned patents has been found quite satisfactory in at least some cases, the use of such apparatus has not been without some problems in others. The discharge of a gaseous flow from a cylindrical tube extending vertically downwardly is radial, thus resulting in velocity components of equal magnitude around the entire periphery of a tube. The consequence is that gaseous flow from tubes which is directed toward the feed end of the treatment zone rather than the discharge end results in velocity components that tend to retard the forward flow of the particles through the treatment zone. And, that gaseous flow radiating from a tube toward the discharge end of the treatment zone provide velocity components that tend to advance the forward movement of the particles through the treatment zone.
Thus, as a result, those particles which are under the influence of either of these velocity components are in the treatment zone for somewhat different residence times. Some particles are in the treatment zone for a somewhat longer residence time than others and other particles are in the treatment zone for a somewhat lesser time than others. Accordingly, whatever the particular manner of treatment involved, the particles are not treated uniformly. Where the treatment involves drying, for example, some particles are dried more or less than others. And, in the case of certain foods, for example, cereals, such a result is not at all desirable, as it effects the texture and crispness of the flakes of cereal involved.
Another problem involved in the use of particle treatment apparatus such as is disclosed in the above-indicated patents, involves the tube structure per se. These tubes, because of their sizes, e.g., 20" long, 3/4" I.D., are rather easily damaged, e.g., bent out of shape, or in some cases, even broken off from the tube sheet. This becomes a particlar problem with those nozzle assembles which are removable, and are removed from the treating apparatus from time-to-time.